Social trends are currently moving toward traditional family values. Ms. Faith Popcorn (that's really her name), president and founder of BrainReserve, a Manhattan firm specializing in detecting consumer trends, attributes America's return to Mom-and-Pop ethics to a backlash from the excesses of the recent past The fear of AIDS is the coup de grace, prompting a return to stable, long-term relationships. But in a PhiladelphiaInquirer interview, Ms. Popcorn warns that as soon as an AIDS cure is